Brewers’ Craft: Baird Lab Report #2: Flourishing Yeast
Hi everyone, long time no see. It’s me, Lab Technician Taiki (27, single). I wrote about yeast naming in my last article around six months ago, but my manager tells me it was univerally panned. I’m not one to let that kind of bad press stop me, so I’m back again and ready to talk about yeast once more!
Yeast is an essential part of brewing beer, but it is also the one ingredient that is still alive when added to the beer. They are lifeforms that grow, propagate, become old, and eventually die. That means they are different from other ingredients in that how they work depends greatly on the conditions they are kept in.
In this article I would like to focus on yeast “propagation,” or the breeding of additional yeast cells. Step on up because tour guide Taiki is here to take you on a journey of yeast propagation here at Baird Beer.
Our yeast is stored at a nearby research facility called Numazu Industrial Research Center. As you can see in the photo, yeast is stored on top of a jelly-like medium in a test tube, which is then stored at a low temperature. There are other storage methods that are even more extreme which we use for backups in case a nameless careless brewer happens to break a test tube. Helpful guys at the research center: thank you. I’ll buy you a beer next time.
That white stuff in the test tube is actually yeast. We transfer it to the wort in this sterile environment.
These yeast in the test tubes are what we might think of as “seeds.” In order to have these guys make good beer for us, we’ll first need them to get out in the world and do a bit of growing first. First, we take some wort (unfermented malt and hop soup) out to the research center. Then we take just a small amount of yeast from the test tube and move it into this wort. Just a tiny amount of yeast gets released into 1 liter of wort. This part of the process is called “inoculation.”
Why use wort, you ask? Wort has a very good balance of the proper nutrients that yeast need to propagate. Also, the hops used in the wort have anti-bacterial properties which will keep away infectious bacteria. This means that the wort is not only ideal food for the yeast, but also the perfect home.
After bringing a small amount of yeast back to the brewery, a rough 10 days begins. First we have to prepare a nice and warm 25 degrees Celsius home for them to live. In order to fuel their propagation in the first 4 days, we also inject oxygen into the wort. As we do this, the yeast feast on the nutrients in the wort and propagate like rabbits. We brewers have to then continually prepare more meals for these insatiable creatures (I guess since they’re propagating it’s understandable). We brewers pretend to be cool and use the English word “propagation” when we talk about this. Working with yeast is the most nerve-wracking part of the job, but it’s also the most fun. We raise these guys to be healthy and strong, and we keep out the bad bacteria. It’s like raising kids!
We start with the initial 1 liter and over a 10 day period we gradually increase the amount of wort. For the final step, we will brew a 6,000 liter batch of wort for the yeast, the largest amount we can brew at once at Baird Brewing. This means that the amount of wort we are using has increased 6,000 times over this period! Let’s see just how much the yeast has propagated; we end up with about 200 kilograms of harvestable yeast, which is around 270 trillion (!) cells. We started with one hundred million cells taken from the research center, so this is an increase of 2,700,000 times. I’m flabbergasted!
Propagation in 1 liter of wort at exactly 25 degrees. It’s busy in there.
The process of turning once little vial of yeast into much more. More yeast, more beer!
This propagated yeast is then harvested from the bottom of the fermentation tanks and transferred to the next tank for another shift. Then we continue this cycle and that’s how beer is made. After a while the yeast will start to get stressed out and become tired, but this is another topic for another day. I’ll see you all later!
Taiki Hashimoto is Baird Brewing’s Lab Technician. He is 27 and single. All invitations for drinks should be directed to [email protected].